WaE: rewrite call of rtl::OUString::operator= with empty string constant ...
WaE: rewrite call of rtl::OUString::operator= with empty string constant ...

... argument as call of rtl::OUString::clear.

Change-Id: I3877a7034edc2cff0509c8a57170228fa1c68685

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core